Liquid crystal displays (LCDs) are widely used in various modern information products, such as notebooks, personal digital assistants, video cameras and the like. An LCD is a passive optical device. Thus a typical LCD needs a backlight module, which provides illumination to enable the LCD to display images.
A typical backlight module includes a light guide plate (LGP) and a plurality of point light sources. The point light sources may be light emitting diodes (LEDs). In certain modern products that use an LCD, the demand for portability of the product is great, and the LCD and its associated components such as the backlight module need to be very thin. Accordingly, the LGP needs to be as thin as possible. Ideally, each LED should be as thin as the LGP, so as to prevent light beams emitted by the LED from leaking. However, in present manufacturing processes this is difficult to achieve, due to limitations inherent in the packaging of an LED. A typical solution to this problem is to form a portion of the LGP adjacent to the LED as thick as the LED itself.
FIG. 6 is a schematic, side view of a conventional backlight module for an LCD. The backlight module 100 includes an LGP 12 and an LED 10. The LGP 12 includes a main body 123 and a light incident portion 120, which are inseparable portions of the one same piece. The main body 123 has a flat plate structure with a thickness less than that of the LED 10, and includes a top light emitting surface 122 and a bottom surface 124. The light incident portion 120 includes a light incident surface 121 adjacent to the LED 10. A thickness of the light incident portion 120 is the same as that of the LED 10, such that the LED 10 can fully abut the light incident surface 121 when the backlight module 100 is assembled. That is, all the light beams emitted by the LED 10 can be received by the LGP 12, and accordingly light beam leakage can be prevented.
When the backlight module 100 is employed in an LCD, a liquid crystal panel (not shown) is provided and disposed on top of the backlight module 100. In operation of the LCD, light beams provided by the LED 10 pass through the light incident portion 120, and emit from the light emitting surface 122 so as to illuminate the liquid crystal panel. Thereby, the liquid crystal panel is able to display images.
In order to prevent light beam leakage, the light incident portion 120 with a thickness greater than the main body 123 is formed. The light incident portion 120 takes up extra space, and limits the compactness of the backlight module 100 and the LCD correspondingly. Moreover, in manufacturing the LGP 12, the light incident portion 120 requires extra material. Thus the cost of the backlight module 100, as well as the LCD, is correspondingly high.
It is, therefore, desired to provide a backlight module having a point light source which can overcome the above-described deficiencies.